electrical
I am wiring up my unfinished basement for rough-in inspection. My understanding is that to wire 30 recessed lights (9w each), I can wire with regular 14/2, in the image below.
However, my PS Knight code book shows me a diagram with a 3 wire cable between fixtures. Is this necessary?
If you can run a new power line to one of the outlets, it may be an easy way to re-use the rest of the existing wiring without having to break walls open too much (less than if you run a new wire from the switch to the ceiling boxes).
The feed would essentially come from the outlets, to the switch, then to the lights/fan, and the existing feed would no longer be used.
You might need to cut an access hole below one of the outlets and then fish a line from underneath, or cut a hole on the wall opposite the outlet, or if you're really lucky, one backs onto an unfinished space. It's very hard to say without actually being there.
Some tips:
Small variation is you could disconnect the outlets from the switch, and keep the circuit you drew for the switches/lights in place exactly as-is. This could be good depending on how you want circuits loaded out (eg, the lights/fan separate from the outlets) and what you have available -- it's very hard to say for certain without being there.
As @Tester101 says, with conventional dimmers, you can only have one dimmer in a circuit if the fixture (or set of fixtures) is being controlled from more than one location.
If you are switching from two locations, you also need to use 3-way switches for both the plain switches and dimmers (many dimmers are 3-way compatible).
There are specialized dimmers that work as master and slave units. These do allow dimming from multiple locations, but you need to use a set of matched units. These are also much more costly than basic 3-way dimmers.
Finally, if you are running remote switches that only connect back to the first set of switches, you need x/4 cable, not x/3. Two wires serve as travelers, one as the common return and one as neutral. While not every switch requires a neutral, code now requires it as a hedge against future active devices. If you do not need the neutral, simply cap it in the box.
Best Answer
You only need three wire between the fixtures if the switch is on a branch off from the lamps
but new requirements for smart switches require 3 wires to the switch in that setup now
That setup is frowned upon these days because CFLs can blink when the switch is off.
You have the supply going direct to the switch (which is the preferred setup) so you only need 2+earth going from the switch to the lamps
If any of those boxes are metal the earth wire should connect to the box. if not just join it with a wire nut as you show.